Q5

Amino Acid Sequence

3D Structure (/structures/AF-Q9UBN7-F1-model_v6.cif)

Function

Deacetylates a wide range of non-histone substrates. Plays a central role in microtubule-dependent cell motility by mediating deacetylation of tubulin. Required for cilia disassembly via deacetylation of alpha-tubulin. Alpha-tubulin deacetylation results in destabilization of dynamic microtubules (By similarity). Promotes deacetylation of CTTN, leading to actin polymerization, promotion of autophagosome-lysosome fusion and completion of autophagy. Deacetylates SQSTM1. Deacetylates peroxiredoxins PRDX1 and PRDX2, decreasing their reducing activity. Deacetylates antiviral protein RIGI in the presence of viral mRNAs which is required for viral RNA detection by RIGI (By similarity). Sequentially deacetylates and polyubiquitinates DNA mismatch repair protein MSH2 which leads to MSH2 degradation, reducing cellular sensitivity to DNA-damaging agents and decreasing cellular DNA mismatch repair activities. Deacetylates DNA mismatch repair protein MLH1 which prevents recruitment of the MutL alpha complex (formed by the MLH1-PMS2 heterodimer) to the MutS alpha complex (formed by the MSH2-MSH6 heterodimer), leading to tolerance of DNA damage. Deacetylates RHOT1/MIRO1 which blocks mitochondrial transport and mediates axon growth inhibition (By similarity). Deacetylates transcription factor SP1 which leads to increased expression of ENG, positively regulating angiogenesis. Deacetylates KHDRBS1/SAM68 which regulates alternative splicing by inhibiting the inclusion of CD44 alternate exons. Deacetylates PRDM16 (By similarity). Acts as a valine sensor by binding to valine through the primate-specific SE14 repeat region. In valine deprivation conditions, translocates from the cytoplasm to the nucleus where it deacetylates TET2 which promotes TET2-dependent DNA demethylation, leading to DNA damage. Promotes odontoblast differentiation following IPO7-mediated nuclear import and subsequent repression of RUNX2 expression (By similarity). In addition to its protein deacetylase activity, plays a key role in the degradation of misfolded proteins: when misfolded proteins are too abundant to be degraded by the chaperone refolding system and the ubiquitin-proteasome, mediates the transport of misfolded proteins to a cytoplasmic juxtanuclear structure called aggresome. Probably acts as an adapter that recognizes polyubiquitinated misfolded proteins and targets them to the aggresome, facilitating their clearance by autophagy. Involved in the MTA1-mediated epigenetic regulation of ESR1 expression in breast cancer.

Mechanism

The ubiquitin-proteasome pathway (UPP) constitutes the principal pathway for protein degradation in eukaryotic cells, mediating the breakdown of target proteins through ubiquitin tagging and subsequent proteasomal degradation. In an ATP-dependent manner, the ubiquitin-activating enzyme (E1) activates ubiquitin (Ub) and conjugates it to a ubiquitin-conjugating enzyme (E2). E3 ligase subsequently catalyzes the transfer of Ub to the target protein, leading to the formation of a polyubiquitin chain that completes the ubiquitination mark. The 19S regulatory particle of the 26S proteasome recognizes this ubiquitination signal and, after deubiquitination, mediates the ATP-dependent delivery of the substrate into the 20S proteasome for degradation

Description

To investigate the mechanism of HyT degradation, we performed immunoblotting assays to evaluate the effects of Q5 on HDAC1 and HDAC6 expression in the presence of MG132 and MLN492. As shown in Fig. 6a, Q5 effectively induces the degradation of both HDAC1 and HDAC6. When Hsp70 inhibitor (Hsp70i) was added, HDAC1 could be reversed but HDAC6 was still degraded. When Hsp90 inhibitor (Hsp90i) was added, the protein levels of both HDAC1 and HDAC6 were restored. When we added both Hsp70 inhibitor and Hsp90 inhibitor, the protein level would completely recover. These results indicated that inhibitors of heat shock proteins Hsp70 and Hsp90 could reverse the down- regulating effect of Q5 by inhibiting protein misfolding and blocking ubiquitination modification [32,33]. Thus, compound Q5 may disrupt the correct folding of HDAC6/HDAC1, making them unstable misfolded proteins, which are then recognized and degraded by the ubiquitin- proteasome system.

Description

Among them, compound Q5 demonstrated the best activity, with an IC50 value of 0.18 μM, which was better than SAHA(IC50=0.23 μM )and SA(The amino-substituted derivative of SAHA, IC50= 0.25 μM).

Description

The protein degradation activities of target compounds against HDAC1/6 were evaluated by western blot analysis in MOLT-4 cells. As shown in Fig. 2a–d, the compounds Q4 and Q5 featuring D-ring-contracted artemisinin moiety (5) showcased maximum HDAC1/6 protein degradation efficacy, and Q5 was slightly more potent than Q4, which is consistent with the anti-proliferative activity in cells (Q5 IC50= 0.18 μM,Q4 IC50=0.42 μM) . For Q5, the Dmax exceeded 87.31% at 100 μM with a half-maximal degradation concentration (DC50 ) of 6.357 μM toward HDAC6 (Fig. 2e–g).

Description

The protein degradation activities of target compounds against HDAC1/6 were evaluated by western blot analysis in MOLT-4 cells. As shown in Fig. 2a–d, the compounds Q4 and Q5 featuring D-ring-contracted artemisinin moiety (5) showcased maximum HDAC1/6 protein degradation efficacy, and Q5 was slightly more potent than Q4, which is consistent with the anti-proliferative activity in cells (Q5 IC50= 0.18 μM,Q4 IC50=0.42 μM) . For Q5, the Dmax exceeded 87.31% at 100 μM with a half-maximal degradation concentration (DC50 ) of 6.357 μM toward HDAC6 (Fig. 2e–g).